1. Field of the Invention
This invention relates to a high intensity magnetic field drum separator having an open magnetic system fixedly arranged within the interior of the drum.
2. Description of the Prior Art
It is usual, with magnetic separators, to differentiate between low intensity magnetic field separators and high intensity magnetic field separators, respectively, which are installed for different types of problems or objectives.
Low intensity magnetic field separators are, as a rule, constructed as drum separators having open magnetic systems, and are predominantly installed for the sorting preparation of strongly magnetic material, or at least magnetic materials having a medium susceptibility, while high intensity magnetic field separators, as a rule, have closed magnetic systems, and are primarily utilized for the preparation of weakly magnetic substances.
High intensity separators are, however, also known which do not differ in the sorting operation substantially from low intensity drum separators. In the case of both systems, a stationary magnetic system is arranged within the interior of a rotating drum.
In contrast, however, with the low intensity separators, in which the entire width of the drum is pentrated or permeated by the magnetic field, in the case of the known high intensity magnetic field drum separators, the magnets are so arranged that the magnetic field is limited to particular zones. Each pair of poles of the magnets which terminate directly on the same within the drum wall form a high intensity magnetic field. In order to draw the lines of force more strongly to the outside, annularly-shaped ferromagnetic outer poles are arranged on the outer periphery of the drum.
With a small scanning mask at the spacing of these outer poles or terminals, great magnetic forces can be attained. The price for this favorable condition is, however, a smaller effective area because of a smaller range, that is, in the end effect a very small preparation capacity, in that, with such high intensity magnetic field separators, the charging of the material to be separated must take place in grooves which convey the material between the outer poles. Magnetizable material adheres to the outer poles, and therebetween to the drum, and afterward is carried, through rotation, out of the area of the magnetic field, released, washed off or stripped off.
Because of the half-open magnetic field between the annularly-shaped poles, in the case of a high intensity magnetic field drum separator, the effective field strength is not as great as with similar separators, so called roller separators, whose operative field is arranged in the closed magnetic system, that is, between two magnetic poles applied to the rotatable drum from the exterior, with an intermediate air gap.
In known high intensity magnetic field drum separators, for example, the field strength is approximately 0.8-1 T (thousand). On the other hand, however, the half-open magnetic field permits separation of coarse grains, for example above 5 mm. Because of the free accessibility of the precipitation wall, the separator is, in addition, uncomplicated in technical operation, sturdy, and permits most easily of being adapted to special requirements, which result in each case through type and grain size of the charging material for a specific case of preparation, particularly in the case of wet magnetic preparation. In this respect, this high intensity magnetic field drum separator is superior to the high intensity magnetic field roller separator.
However, in addition to the previously mentioned low capacity, a further particular disadvantage arises in the known high intensity magnetic field drum separator, in that it has developed that the drum separator is not to be used for the separation of ores having grain sizes of, at least in part, far below 100 .mu.m, which has recently become more and more important.